The Seoul National University AGN Monitoring Project IV: H\(\alpha\) reverberation mapping of 6 AGNs and the H\(\alpha\) Size-Luminosity Relation

• Published in: arXiv.org 2023-06
• Main Authors: Cho, Hojin, Jong-Hak Woo, Wang, Shu, Son, Donghoon, Shin, Jaejin, Rakshit, Suvendu, Barth, Aaron J, Bennert, Vardha N, Gallo, Elena, Hodges-Kluck, Edmund, Treu, Tommaso, Hyun-Jin Bae, Cho, Wanjin, Foord, Adi, Geum, Jaehyuk, Jadhav, Yashashree, Jeon, Yiseul, Kabasares, Kyle M, Kang, Daeun, Kang, Wonseok, Kim, Changseok, Kim, Donghwa, Kim, Minjin, Kim, Taewoo, Huynh Anh N Le, Malkan, Matthew A, Mandal, Amit Kumar, Park, Daeseong, Park, Songyoun, Hyun-il Sung, Vivian, U, Williams, Peter R
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Luminosity; Monitoring
• ISSN: 2331-8422

The broad line region (BLR) size-luminosity relation has paramount importance for estimating the mass of black holes in active galactic nuclei (AGNs). Traditionally, the size of the H\(\beta\) BLR is often estimated from the optical continuum luminosity at 5100\angstrom{} , while the size of the H\(\alpha\) BLR and its correlation with the luminosity is much less constrained. As a part of the Seoul National University AGN Monitoring Project (SAMP) which provides six-year photometric and spectroscopic monitoring data, we present our measurements of the H\(\alpha\) lags of 6 high-luminosity AGNs. Combined with the measurements for 42 AGNs from the literature, we derive the size-luminosity relations of H\(\alpha\) BLR against broad H\(\alpha\) and 5100\angstrom{} continuum luminosities. We find the slope of the relations to be \(0.61\pm0.04\) and \(0.59\pm0.04\), respectively, which are consistent with the \hb{} size-luminosity relation. Moreover, we find a linear relation between the 5100\angstrom{} continuum luminosity and the broad H\(\alpha\) luminosity across 7 orders of magnitude. Using these results, we propose a new virial mass estimator based on the H\(\alpha\) broad emission line, finding that the previous mass estimates based on the scaling relations in the literature are overestimated by up to 0.7 dex at masses lower than \(10^7\)~M\(_{\odot}\).